1. Field of the Invention
The present invention relates to an ink-jet recording method which enables formation of an image with high optical density and high resolution, particularly to an ink-jet recording method which enables recording of an image excellent in light-transmissivity or surface gloss.
The present invention also relates to a color image-forming method employing the above recording method.
2. Related Background Art
Various recording mediums are used for ink-jet recording, including coated-paper sheets, glossy-paper sheets, OHP-recording films (recording films for overhead projectors), etc. An example of the coated paper is the one disclosed in Japanese Patent Publication No. 3-26665 which comprises a base paper sheet, and a coating layer thereon composed of fine powdery silica and a water-soluble binder such as polyvinyl alcohol. An example of the glossy paper is the one disclosed in Japanese Patent Publication No. 3-25352 which comprises a cast-coated paper sheet, and a surface layer composed of polyvinyl alcohol of a saponification degree of 50 to 90 mol % and a crosslinking agent. An example of the OHP-recording sheets is the one which is disclosed by Japanese Patent Application Laid-Open No. 60-220750 comprising a polyester film and a hydrophilic surface layer thereon composed of a water-soluble polyvinyl alcohol of a saponification degree of 70 to 90 mol %.
With improvements in performance of ink-jet recording apparatuses in recording speed, multiple color recording and so forth, the recording medium therefor is required to be improved to have the properties below simultaneously:
(1) The recording medium has higher ink-absorbency (a larger ink absorption capacity, and quicker ink absorption). PA0 (2) The recorded dots on the recording medium have high optical density with distinct circumference. PA0 (3) The recorded dots on the recording medium have a shape approximate to a true circle with smooth circumference. PA0 (4) The recording medium changes little its properties and does not curl with changes of temperature and humidity. PA0 (5) The recording medium does not cause blocking. Further, the recording medium is required to have storability as below: PA0 (6) The recorded image is stable and does not deteriorate in long-term storage (particularly under a high temperature and a high humidity). PA0 (7) The recording medium itself is stable and does not deteriorate in long-term storage (particularly under a high temperature and a high humidity). PA0 (a) a coating layer mainly composed of polyvinyl alcohol of a saponification degree of from 75 to 98 mol % and a polymerization degree of from 100 to 500, or a derivative thereof, PA0 (b) a coating layer mainly composed of a copolymer of vinylpyrrolidone with a vinyl monomer having a hydrophobic group, and a polyalkylene oxide or a derivative thereof, and PA0 (c) a coating layer mainly composed of an aromatic polyvinylacetal resin, and a polyalkylene oxide or a derivative thereof. PA0 (a) a coating layer mainly composed of polyvinyl alcohol of a saponification degree of from 75 to 98 mol % and a polymerization degree of from 100 to 500, or a derivative thereof, PA0 (b) a coating layer mainly composed of a copolymer of vinylpyrrolidone with a vinyl monomer having a hydrophobic group, and a polyalkylene oxide or a derivative thereof, and PA0 (c) a coating layer mainly composed of an aromatic polyvinylacetal resin, and a polyalkylene oxide or a derivative thereof.
For ink-jet recording of a transparent image for OHP or of an image with high surface gloss, a light-transmissive recording sheet or a glossy recording sheet (or glossy paper) is needed. Such a recording sheet has conventionally an ink-receiving layer mainly composed of a hydrophilic resin like polyvinyl alcohol, as mentioned above, to minimize diffusion reflection of incident light on the recording face, or to form a highly light-transmissive coating layer.
With the progress of ink-jet recording in recording speed, recording density, and color printing technique, deterioration of image quality caused by insufficient ink fixation has become a serious problem, particularly in a recording method for formation of a light-transmissive image or of a glossy image. The recording face of the recording sheet for such uses, which is not porous unlike usual coated paper or plain paper, does not have sufficient ink absorbency. Therefore, staining of the image is caused by running of ink, and unevenness of the image density is caused by coalescence of unfixed ink droplets (beading) on the recording face. In color printing, dulling of color is caused by color mixing at the color border (border bleeding) between different colors. These phenomena decrease significantly the sharpness of the image.
The recording medium described in Japanese Patent Publication No. 3-29596, which has an ink-receiving layer mainly composed of polyvinyl-pyrrolidone, has relatively high ink absorbency at a normal temperature and a normal humidity, but has disadvantages of extremely low ink-drying speed and liability of blocking at a higher temperature and a higher humidity, and low resistance to scratching owing to low mechanical strength of the recording surface.
In the recording method employing the above light-transmissive or glossy recording sheet, no effective recording sheet has been obtained which solves the problems of beading and border bleeding in spite of the effort to improve the recording sheet. Furthermore, few studies have been made to solve the above problems by improvement of both the recording sheet and the ink in combination.